Semiquantitative Assessment of First-Pass Renal Perfusion at 1.5 T: Comparison of 2D Saturation Recovery Sequences With and Without Parallel Imaging
Henrik J. Michaely1,
Harald Kramer1,
Niels Oesingmann2,
Klaus-Peter Lodemann3,
Maximilian F. Reiser1 and
Stefan O. Schoenberg1
1 Department of Clinical Radiology, University of Munich, Grosshadern-Campus,
Marchionistrasse 15, Munich, Germany, 81377.
2 Siemens Medical Solutions, Malvern, PA.
3 Bracco-Altana Pharma, Konstanz, Germany.
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Fig. 1B —28-year-old man in good health. Graph shows measured mean
peak signal intensities in aorta and both kidneys. True fast imaging with
steady-state free precession (FISP) sequence yields highest absolute signal
from enhanced kidneys and enhanced aorta. Turbo FLASH sequences with and
without parallel imaging (PI) perform in similar way. AU = arbitrary
units.
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Fig. 1C —28-year-old man in good health. Graph shows calibration curve
with measured signal intensities from first five vials (0.032-1.0 mmol/L of
gadobenate dimeglumine). Peak signal intensity measured in aorta and kidneys
(B) are well within increasing part of calibration curve.
T2*-related loss of signal intensity can therefore safely be ruled
out. Solid line indicates regression for true FISP sequence; dashed line,
regression for turbo FLASH sequence; dotted line, regression for turbo FLASH
sequence with parallel imaging.
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Fig. 3A —25-year-old man in good health. Signal intensity-time curves
for three MRI sequences. Dotted lines indicate true fast imaging with
steady-state free precession (FISP), solid gray lines indicate turbo fast
low-angle shot (FLASH) without parallel imaging, and solid black lines
indicate turbo FLASH with parallel imaging. Graph shows marked differences in
configuration of first pass peak. AU = arbitrary units.
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Fig. 3B —25-year-old man in good health. Signal intensity-time curves
for three MRI sequences. Dotted lines indicate true fast imaging with
steady-state free precession (FISP), solid gray lines indicate turbo fast
low-angle shot (FLASH) without parallel imaging, and solid black lines
indicate turbo FLASH with parallel imaging. Gamma variate fit of curves in
A. True FISP sequence yielded lowest maximal signal intensity and
slowest upslope of curve. Mean transit time and time to peak were equal for
all techniques. Scale of x-axis is slightly different from that in
A.
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Fig. 4A —Comparison of sequences. Graph shows comparison of measured
signal-to-noise ratio (SNR) at baseline and peak enhancement in renal cortex
and abdominal aorta. True fast imaging with steady-state free precession
(FISP) sequence yields highest SNR. Turbo fast low-angle shot (FLASH)
sequences with and without parallel imaging (PI) behave similarly to each
other.
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Fig. 4B —Comparison of sequences. Graph shows delta ratio comparisons
for three sequences. True FISP yielded highest SNR at baseline and during peak
enhancement. Relative enhancement—that is, delta ratio—however,
was only 3.2 for true FISP. Turbo FLASH sequences had 59% higher delta ratios
of 5.1 with and 5.0 without parallel imaging.
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Fig. 5D —29-year-old man in good health. Unenhanced (D), early
arterial phase (E), and medullary phase (F) MR images obtained
with turbo FLASH sequence with parallel imaging show higher noise level than
A-C.
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Fig. 5E —29-year-old man in good health. Unenhanced (D), early
arterial phase (E), and medullary phase (F) MR images obtained
with turbo FLASH sequence with parallel imaging show higher noise level than
A-C.
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Fig. 5F —29-year-old man in good health. Unenhanced (D), early
arterial phase (E), and medullary phase (F) MR images obtained
with turbo FLASH sequence with parallel imaging show higher noise level than
A-C.
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Fig. 5G —29-year-old man in good health. Unenhanced (G), early
arterial phase (H), and medullary phase (I) MR images obtained
with true fast imaging with steady-state free precession sequence yield best
signal-to-noise ratio, but because of higher background signal intensity,
kidneys are difficult to differentiate.
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Fig. 5H —29-year-old man in good health. Unenhanced (G), early
arterial phase (H), and medullary phase (I) MR images obtained
with true fast imaging with steady-state free precession sequence yield best
signal-to-noise ratio, but because of higher background signal intensity,
kidneys are difficult to differentiate.
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Fig. 5I —29-year-old man in good health. Unenhanced (G), early
arterial phase (H), and medullary phase (I) MR images obtained
with true fast imaging with steady-state free precession sequence yield best
signal-to-noise ratio, but because of higher background signal intensity,
kidneys are difficult to differentiate.
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Fig. 6A —29-year-old man in good health. MR image obtained with single
true fast imaging with steady-state free precession sequence shows
susceptibility artifacts that occur when kidney is close to air-filled large
bowel. Margins of renal cortex (arrows) are not clearly defined on
either side.
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Fig. 6B —29-year-old man in good health. Medullary phase (D) MR
images obtained with turbo fast low-angle shot sequence with parallel imaging
show typical bandlike reconstruction artifact (arrows). Artifacts
were seen especially in late phases of perfusion measurement after
intravascular concentration of contrast agent had markedly decreased.
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Fig. 6C —29-year-old man in good health. Medullary phase (D) MR
images obtained with turbo fast low-angle shot sequence with parallel imaging
show typical bandlike reconstruction artifact (arrows). Artifacts
were seen especially in late phases of perfusion measurement after
intravascular concentration of contrast agent had markedly decreased.
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Fig. 6D —29-year-old man in good health. Medullary phase (D) MR
images obtained with turbo fast low-angle shot sequence with parallel imaging
show typical bandlike reconstruction artifact (arrows). Artifacts
were seen especially in late phases of perfusion measurement after
intravascular concentration of contrast agent had markedly decreased.
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Copyright © 2007 by the American Roentgen Ray Society.
